Science Motivation for the CIDER 2017 Summer Program

We expect to develop a schedule where we investigate the subduction zone systematically from the incoming plate and the shallow forearc to the processes in the deep slab interior and those of the mantle wedge and overriding plate.

Overarching questions are diverse and include:

“What is the hydration state of the incoming plate?”,

“How does subduction initiate?”,

“What is the role of the accretionary prism and what controls whether margins are erosional or accretional?”

“What controls the distribution of seismic and aseismic slip along the shallow thrust zone?”

“Why do some subduction zones show no large thrust earthquakes?”

“What controls the spectrum of fault creep and rupture including episodic tremor and slip?”

“How do metamorphic reactions control the release of fluids and seismicity?”

“How do fluids leave the slab and trigger wedge melting?”

“How do continental arcs evolve and contribute to the formation of the continental crust?”

“What leads to the spectrum of arc volcanic unrest and activity?”

“What are the relative rates of the main processes occurring at subduction zones?”

"Why do some subducted slabs stagnate at 660 km or 1000 km depth?"

We plan to tap into the research expertise involved with the geophysical and geochemical work sponsored by Earthscope and GeoPRISMS/MARGINS and use in particular (although not exclusively) the Cascadia, Alaska-Aleutian, Japan, Central America and Izu-Bonin-Mariana (IBM) subduction zones as case studies. Cascadia offers a unique perspective as it is one of the warmest subduction zones on the planet. The Alaska-Aleutian arc offers strong transitions in driving functions including changes in age, speed and convergence direction along the arc, and depth to the slab surface. IBM offers a classic island-arc setting with an active backarc spreading center and an apparent absence of large thrust earthquakes. Japan is by far the best instrumented subduction zone on the planet and offers contrasts between very young and warm subduction in the South and mature subduction to the North. Central America in terms of thermal properties intermediate and has been exposed well by long-term collaborative research between Central American, US and German scientists.